The present invention relates to medical diagnostics and in particular to a method and system for constructing and displaying three-dimensional images.
In the medical field, it is common to use ultrasound diagnostic equipment to view internal organs of a subject. For example, in diagnosing prostate cancer, a diagnostician uses transrectal ultrasound (TRUS) to identify whether lesions are present as well as to determine the location, size and extent of lesions if present. Conventional ultrasound diagnostic equipment typically comprise an ultrasound probe for transmitting ultrasound signals into the subject and receiving reflected ultrasound signals therefrom. The reflected ultrasound signals received by the ultrasound probe are processed and a two-dimensional image of the target under examination is formed.
Unfortunately, this conventional equipment produces two-dimensional images even though the target under examination is three-dimensional. Also, the two-dimensional images represent a single thin plane taken at an arbitrary angle to the target making it very difficult to localize the image plane in the target and very difficult to reproduce an image at a particular location at a later time.
In U.S. application Ser. No. 08/419,049 and U.S. Pat. No. 5,454,371, assigned to the assignee of the present application, the contents of which are incorporated herein by reference, three-dimensional ultrasound imaging systems are described. Although, these systems overcome disadvantages associated with the prior art, improvements to enhance imaging and to increase the speed by which three-dimensional images can be generated from two-dimensional ultrasound images are continually being sought.
It is therefore an object of the present invention to provide a novel system and method for generating a three-dimensional image from a succession of two-dimensional images, and a novel ultrasound imaging system.
According to one aspect of the present invention there is provided a three-dimensional imaging system for acquiring a succession of two-dimensional images of a target volume represented by an array of pixels I(x,y,z) into a three-dimensional image represented by a volumetric image array V(x,y,z) comprising:
scanning means to scan said target volume along a predetermined geometric scanning path and generate a succession of digitized two-dimensional images thereof representing cross-sections of said target volume of a plurality of planes spaced along said scanning path;
memory storing said succession of digitized two-dimensional images together with other related image data defining the location of said two-dimensional images in said memory and defining interpretation information relating to the relative position of pixels within said two-dimensional images and to the relative position of pixels in adjacent two-dimensional images within said target volume;
transformation means receiving said digitized two-dimensional images and said other related image data and transforming said two-dimensional images and said other related image data into a volumetric image array; and
display means to generate a three-dimensional image of said target volume from said volumetric image array.
In one embodiment, the geometric scanning path is linear. In this instance, the cross-sections are tilted with respect to an axis normal to the linear scanning path. The transformation means transforms the two-dimensional images and the other related image data into the volumetric image array using a shear transformation. The other related image data includes an address pointer indicating the location of the memory of which the two-dimensional image data begins together with data representing the number of pixels along x and y axis of each two-dimensional image. The other related image data also includes physical distance values between adjacent pixels in each of the two-dimensional images as well as the distance between corresponding pixels in adjacent two-dimensional images together with the tilt angle of the cross-sections.